Molecular genetics of animal models of retina degeneration
Abstract
Animal models for retinal degeneration of genetic origin are important tools for studying the corresponding human diseases. They are also of interest to basic research in vision as in vivo systems in which a particular photoreceptor-specific gene product is either absent or present in an aberrant form, so that information about the function of that gene may be inferred. In this study, I attempted to elucidate the underlying genetic defects that program the photoreceptor cell death in two such models: the rod-cone dystrophic (rcd 1) Irish setter dog and the rd mouse. The strategy used is that of a candidate gene approach. Considerable effort was devoted initially to developing molecular probes for the candidate genes, that is, photoreceptor specific genes that had been implicated in the disease process by biochemical studies. As an outcome, cDNAs encoding the $\alpha$, $\beta$, and $\gamma$ subunits of rod cGMP-phosphodiesterase and the large subunit of cone phosphodiesterase were isolated from bovine retinal cDNA libraries and characterized. These molecular probes, or in some cases probes previously available, were used to examine the genome of the affected animals for any clues of a mutation. I first examined the opsin gene from normal and dystrophic Irish setter dogs, determined the coding and exon-intron junctional sequences of both and by comparison, showed that the opsin gene is not the site of mutation in this animal. Next I examined the genes coding for PDE subunits in the genome of the rd mouse. Genomic Southern blotting with $\beta$-subunit probe showed distinct restriction fragment length polymorphisms that clearly segregate with the rd allele. The $\beta$-subunit cDNAs from wild type and heterozygous mice were isolated and sequenced. The combined data demonstrate that the rd locus in mouse is the structural gene for the $\beta$-subunit of rod photoreceptor cGMP-phosphodiesterase.
Degree
Ph.D.
Advisors
Applebury, Purdue University.
Subject Area
Molecular biology|Genetics
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